He had no comment for waiting reporters as he was whisked away from Bray Garda Station in a car driven by a relative some 31-and-a-half hours after he was taken into custody.

The 61-year-old was questioned by detectives from the Garda Bureau of Fraud Investigation under legislation relating to false accounting.

After his release, gardai said their investigation into alleged financial irregularities at Anglo Irish was continuing and a file would be prepared for the Director of Public Prosecutions.

Detectives are expected to quiz several other senior bankers associated with Mr FitzPatrick in the coming weeks as their inquiry enters a crucial stage. The investigation has been ongoing for over a year.

Mr FitzPatrick emerged from the garda station at 1.50pm yesterday wearing a dark suit, mauve tie and blue shirt.

A large media presence and several onlookers watched as he sat into a 2001 Volkswagen Golf and was driven to his home in nearby Greystones.

He had been questioned for almost 24 hours in total by teams of fraud detectives.

The rest of his time in custody was spent sleeping or taking short breaks.

Over 100 people have already been questioned as part of the Anglo Irish probe.

But Mr FitzPatrick is the first of these to have been arrested.

A number of other key figures closely associated with Mr FitzPatrick and with knowledge of the inner workings of the bank will be quizzed in the coming weeks.

It remains to be seen whether others will also be arrested or will be simply asked to give statements voluntarily.

Gardai and the Office of the Director of Corporate Enforcement have been investigating three main issues at the bank. They are:

The movement of €7.45bn in deposits between Anglo Irish and Irish Life & Permanent to bolster Anglo's books.

The concealment from shareholder of loans, at one stage totalling €129m, to Mr FitzPatrick for eight years.

The controversial loan of €450m to a "golden circle" of 10 bank clients so they could buy a 10pc share in the bank.

During his time in custody, Mr FitzPatrick was questioned under Section 10 of the Criminal Justice (Theft and Fraud Offences) Act, which relates to false accounting. Under that section of the act, it is an offence to dishonestly make a gain for oneself or cause a loss to another by falsifying an account, failure to complete an account or knowingly giving false information for accounting purposes.

The offences covered by this section of the act carry a penalty following conviction on indictment of up to 10 years in prison.

Seized

The arrest of Mr FitzPatrick is the biggest public development in the investigation since Anglo Irish headquarters were raided by gardai on February 24 last year.

Officers spent four days at the bank, and seized computers and several boxes of documents.

The investigative progress was subsequently delayed by wrangles over whether certain documents were legally privileged.

Mr FitzPatrick's arrest came just a week after Anglo Irish began legal proceedings against him in a bid to recover €70m in loans he received from the bank. Mr FitzPatrick stopped servicing the loans last year.

He has invested in a number of foreign business ventures, including oil exploration in Nigeria and a casino in Macau.